1. Field of the Invention
The present invention broadly relates to dielectric resonator devices and, more particularly, to dielectric resonator devices used in a millimetric wave or microwave band.
2. Description of the Related Art
Hitherto, as comparatively high power microwave band dielectric resonators, TE01* mode dielectric resonators and TE mode dielectric resonators are used. In the TE01* mode dielectric resonators, a cylindrical or tubular dielectric member is disposed inside a shielding case. In the dielectric TM mode dielectric resonators, an electrode is disposed on the surface of a dielectric plate or a dielectric member. In particular, since the TE mode dielectric resonators are compact and obtain a high nonloaded Q (Q.sub.o) factor, they are used in, for example, antenna sharing units of a base station in a mobile communication cellular system.
In the TM mode dielectric resonators, a displacement current flows along the electric field distribution, while a current flows in the electrode formed on the surface of the resonator. Thus, the Q.sub.o factor of the resonator is lowered due to conduction losses of the electrode. Accordingly, when a dielectric resonator is miniaturized using a dielectric material having a high relative dielectric constant, the current density of the surface of the resonator increases, thereby lowering the resonator Q.sub.o factor. Namely, the miniaturization of the dielectric resonator and the increased Q.sub.o factor have a trade off relationship.